False color plots of the ion density distribution for initial . The time since ionization is indicated. The initial localized density depletion splits to produce two ion holes propagating away from plasma center. (Scale bar = 2 mm, density given in .)
Ion gap splitting and hole propagation for initial electron temperatures of 25 K (a) and 55 K (b). Data are slices along a line perpendicular to the initial density depletion through the center of the plasma, integrated over a width of , with plasma size varying from ∼1.4 to 2 mm. The results of the hydrodynamic simulation and hole positions extracted from fits to the density profile are also shown. Traces are offset proportional to evolution time, t. (c) Positions of the holes with fits to Eq. (14) . The average values extracted from the hole propagation are and .
Evolution of the plasma size for initial peak density and initial electron temperature determined by the photoionization laser indicated in the legend. The plasma size was measured from the Gaussian fits neglecting the small perturbation of the ion holes (see Fig. 2 ) and fit to Eq. (7) . The extracted values of from expansion are and .
Measured extracted from the motion of the ion holes (Eq. (14) ). The expected electron temperature is the value set by the wavelength of the photoionizing laser. Simulation and experimental points are both extracted the same way from the density profiles, and each point is an average of the measurement for left and right-going holes. The dashed line is provided as a guide to the eye. Error bars here and elsewhere in the paper are 95% confidence intervals.
Spatially resolved regional spectra for an unperturbed (blue) and perturbed (red) plasma with , and . Each region is in length perpendicular and parallel to the gap. Region 0 represents the center of the plasma, and regions are spaced every to the right of center with respect to the orientation of Fig. 1 . Time since ionization is indicated on the right. The amplitudes of all signals are scaled by a universal factor.
Average ion velocity and temperature for regions in the vicinity of the gap. Each region is perpendicular to the gap and the same parallel to it. Region 0 represents the center of the plasma, and subsequent regions are each shifted to the right by with respect to the orientation of Fig. 2 . Results of the simulation are also shown. Note the presence of negative velocities, which indicate ion flow towards the center as the ion hole passes as it moves away from the center.
Mean-free-paths and timescales for Strontium ion-ion collisions, at a range of ion temperatures and multiples of the ion thermal speed, for a hole density of .
Mean-free-paths and timescales for electron-electron collisions, at a range of electron temperatures and multiples of the electron thermal speed, for a hole density of .
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